平成 27 年度

離島における地熱資源の活用可能性調査
報告書目次

第1章

調査研究の概要 ··································································· 11.1

背景と調査目的 ···································································· 11.2

本年度の調査研究内容 ······························································ 2

1.3

調査研究の実施経過 ································································ 31.3.1

調査研究体制の組織化 ·························································· 3

1.3.2

調査研究実施状況 ······························································ 31.4

調査成果概要 ······································································ 51.4.1

有人離島の電力施設状況の調査結果 ·············································· 51.4.2

内燃力発電所を有する有人離島の地熱ポテンシャル関連情報の調査結果 ·············· 51.4.3

内燃力発電所を有する有人離島の地熱発電導入の可能性の概略検討結果 ··············61.4.4

次年度調査計画案の検討結果 ···················································· 6第２章

内燃力発電所を有する有人離島の電力施設状況等の調査 ······························· 82.1

調査内容・調査方法 ································································ 82.1.1

調査内容 ······································································ 82.1.2

調査方法 ······································································ 82.2

離島の内燃力発電所の施設状況 ······················································ 82章

参考文献 ········································································ 17第３章

内燃力発電所を有する有人離島の地熱ポテンシャル関連情報の調査 ···················· 183.1

調査内容・調査方法 ······························································· 183.1.1

調査内容 ····································································· 18

3.1.2

調査方法 ····································································· 18

3.2

北海道電力管轄の有人離島の地熱ポテンシャル関連情報 ······························· 18

3.2.1

礼文島（れぶんとう） ························································· 18

3.2.2

利尻島（りしりとう） ························································· 19

3.2.3

焼尻島（やぎしりとう） ······················································· 193.2.4

奥尻島（おくしりとう） ······················································· 20

3.3

東京電力管轄の有人離島の地熱ポテンシャル関連情報 ································· 223.3.1

新島・式根島（にいじま・しきねじま） ········································· 223.3.2

神津島（こうづじま） ························································· 27

3.3.3

三宅島（みやけじま） ························································· 30

3.3.4

八丈島（はちじょうじま） ····················································· 33

3.3.5

利島（としま） ······························································· 35

3.3.6

青ヶ島（あおがしま） ························································· 35

3.3.7

御蔵島（みくらじま） ························································· 35

3.3.8

伊豆大島（いずおおしま） ····················································· 36

3.3.9

父島・母島（ちちじま・ははじま） ············································· 40

3.4東北電力・北陸電力管轄の有人離島の地熱ポテンシャル関連情報 ······················· 40

3.4.1

佐渡島（さどがしま） ························································· 41

3.4.2

粟島（あわじま） ····························································· 44

3.4.3

飛島（とびしま） ····························································· 44

3.4.4

舳倉島（へぐらじま） ························································· 443.5

中国電力管轄の有人離島の地熱ポテンシャル関連情報 ································· 45

3.5.1

隠岐諸島（おくしょとう） ····················································· 45

3.5.2

見島（みしま） ······························································· 45

3.6九州電力管轄の有人離島の地熱ポテンシャル関連情報 ································· 46

3.6.1小呂島（おろのしま） ························································· 46

3.6.2

対馬（つしま） ······························································· 46

3.6.3

壱岐（いき） ································································· 46

3.6.4

五島（ごとう） ······························································· 47

3.6.5

甑島（こしきじま） ··························································· 50

3.6.6

種子島（たねがしま） ························································· 50

3.6.7

竹島（たけしま） ····························································· 50

3.6.8

黒島（くろしま） ····························································· 51

3.6.9

薩摩硫黄島（さつまいおうじま） ··············································· 51

3.6.10 口永良部島（くちのえらぶじま） ··············································· 58
3.6.11 中ノ島（なかのしま） ························································· 61
3.6.12 口之島（くちのしま） ························································· 64

3.6.13 悪石島（あくせきじま） ······················································· 67
3.6.14 小宝島（こだからじま） ······················································· 67
3.6.15 宝島（たからじま） ··························································· 67
3.6.16 平島（たいらじま） ··························································· 68
3.6.17 諏訪之瀬島（すわのせじま） ··················································· 68
3.6.18 奄美大島（あまみおおしま） ··················································· 69
3.6.19 喜界島（きかいじま） ························································· 69
3.6.20 徳之島（とくのしま） ························································· 69
3.6.21 沖永良部島（おきのえらぶじま） ··············································· 70
3.6.22 与論島（よろんとう） ························································· 70
3.7沖縄電力管轄の有人離島の地熱ポテンシャル関連情報 ································· 71

3.7.1

久米島（くめじま） ··························································· 71

3.7.2

渡嘉敷島（とかしきじま） ····················································· 71

3.7.3

渡名喜島（となきじま） ······················································· 71

3.7.4

粟国島（あぐにじま） ························································· 72

3.7.5

南大東島（みなみだいとうじま） ··············································· 72

3.7.6

北大東島（きただいとうじま） ················································· 72

3.7.7

宮古島（みやこじま） ························································· 73

3.7.8

多良間島（たらまじま） ······················································· 73

3.7.9

石垣島（いしがきじま） ······················································· 73

3.7.10 波照間島（はてるまじま） ····················································· 74
3.7.11 与那国島（よなぐにじま） ····················································· 74
3.8

有人離島の地熱ポテンシャル関連情報のまとめ ······································· 753章

参考文献 ········································································ 79

第４章

内燃力発電所を有する有人離島の地熱発電導入の可能性の概略検討 ···················· 814.1

内燃力発電離島に対する地熱発電導入の判断指標の概略検討 ··························· 81

4.1.1

検討方針 ····································································· 81

4.1.2

内燃力発電所の発電単価について ··············································· 81

4.2

電力会社、自治体の地熱発電導入に対する意見 ······································· 85

4.2.1

電力会社・経済産業局へのヒアリング ··········································· 85

4.1.2

自治体へのヒアリング ························································· 85

4.3

地熱発電導入可能性のある離島の抽出 ··············································· 86

第５章

次年度調査計画案の検討 ·························································· 91

5.1

次年度調査計画の策定方針 ························································· 91

5.2

離島スマートグリッド構想の次年度調査計画案 ······································· 91

5.3

周辺離島への余剰エネルギー供給構想の次年度調査計画案 ····························· 92

第６章

まとめ·········································································· 94

6.1

有人離島の電力施設状況の調査結果 ················································· 946.2

内燃力発電所を有する有人離島の地熱ポテンシャル関連情報の調査結果 ················· 946.3

内燃力発電所を有する有人離島の地熱発電導入の可能性の概略検討結果 ················· 95

6.4

次年度調査計画案の検討結果 ······················································· 96

背景と調査目的2011 年 3 月の東日本大震災後、エネルギー政策の大幅な見直しが求められ、電力需給の逼迫が大きな社会問題となっており、太陽光、風力、水力および地熱などの再生可能エネルギーの利用拡大の機運が高まっている。特に、国内資源量が世界第 3 位である地熱資源は、エネルギーセキュリティ、地球温暖化対策、ベース電源確保の観点から開発への期待が高まっており、国の支援も拡大されてきている。その結果、山葵沢地熱発電所などの数 10MW 規模の大規模地熱開発が計画され推進されはじめると共に、数 MW 規模の中規模地熱開発、および数 10kW～数 100kW 規模の小規模な地熱開発も多数計画されてはいるが、純国産の地熱資源のさらなる利用拡大が望まれているものと考えられる。このため、地熱資源の新たな開発・利用拡大先を検討した結果、わが国に数多くある離島への導入可能性に着目したのである。
本土（北海道、本州、四国、九州、沖縄本島）を除くと、わが国には離島は 6,800 超、有人離島も 400 超あり、相当数の有人離島では、発電方式として図 1.1-1 のディーゼル発電が採用されている。図のように、ディーゼル発電は重油などを本土から離島に輸送して離島内で発電するもので、出力に対して小型軽量であり、始動性がよく熱効率が高い等の長所があり、離島の電源に多く用いられている。しかし、離島でのディーゼル発電は、発電コストが本土に比べて相当高い場合が多く、電力会社の経済的負担になっていると共に、温暖化ガスの排出という今後改善が望ましい課題もある。
我が国には火山や温泉を有す離島も多く、地熱資源が賦存する有人離島は多いものと推察されるので、地熱発電を導入できれば、発電コストの削減と温暖化ガスの削減が行なえる可能性があり、離島の活性化にも貢献できると考えた。地熱発電は出力一定のベース電源と位置付けられ、本土の電力系統から独立した離島には、出力変動の大きい風力や太陽光よりも適したエネルギーであることも、離島に対する地熱発電導入の可能性検討を行う理由の一つである。
以上のように、本調査研究では、有人離島への地熱発電導入の可能性を明確化・具体化することを最終目標としており、調査研究期間は平成 27 年度（初年度）、28 年度（次年度）の 2 年間で計画した。